Installation for increasing usable range along axial direction of light source

ABSTRACT

An installation for increasing the usable range along the axial direction of a light source. The installation has a light source and an optical sensor. The light source generates a sense image. The optical sensor further has a sensor and a transparent panel. The sensor is responsible for detecting the image generated by the light source so that a sense image is created. The transparent panel is positioned between the sensor and the light source. A coating on the transparent panel modifies the light transparency along the axial direction of the light source such that light transparency is lower in the middle compared with the ends.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 88222561, filed Dec. 18, 1999.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an installation capable of increasingthe usable range of a light source. More particularly, the presentinvention relates to an installation capable of increasing the usablerange along the axial direction of a light source.

2. Description of Related Art

The operating principles of most image-extraction instruments, such asscanners and digital cameras, are very similar. Common features ofimage-extraction instruments include the use of a light source toproduce an optical image and the passing of an optical image through anoptical transmission system to an optical sensor. In general, theoptical sensor is a charge couple device (CCD).

However, the longitudinal light source of a scanner has one majordrawback, namely, brightness level along the central portion of thelight axis is usually higher than along the adjacent sides. Hence, animage produced by the light source is brighter in the middle whiledimmer along the edges. Since a scanner depends on brightness contrastto operate, a conventional scanner has poorer contrast near the twoedges of the light axis. To preserve quality of the scan image, asection near the edge regions is often unused.

Hence, reducing brightness level variation along the axial direction ofa light source has become one of the major improvement targets. Forexample, in Taiwan patent publication no. 244013 entitled ‘Improved lampshade compensation of an optical scanner’, brightness variation alongthe light axis is improved by modifying the lamp shade structure.However, the invention requires specially made components, and hence maylead to an increase in production cost.

In Taiwan patent publication no. 352886 entitled ‘A lens structure andits integration with an image-reading device’, another method ofimproving brightness level along the axial direction of a light sourceis proposed. By changing the degree of reflectivity of a coated film onthe reflecting lens inside the scanner, brightness level variation isreduced. However, the reflectivity of more than one reflecting lensneeds to be modified, thereby increasing the production cost necessaryfor achieving the results. In addition, the method is not suitable forother optical sensing devices besides a scanner.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide aninstallation for increasing the scanning range along the axial directionof a light source by changing the light transparency of the transparentpanel leading, to an optical sensor. In addition, the installation canbe applied to other optical devices besides a scanner,such as a digitalcamera.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, theinvention provides an installation for increasing the scanning range ofa light source. The installation includes a light source and an opticalsensor. The light source is used as a source for generating the image tobe detected. The optical sensor includes a sensor and a transparentpanel. The transparent panel is positioned between the sensor and thelight source. Furthermore, the transparent panel also has a long axisthat runs from edge to edge passing through the panel. The sensorreceives an optical image formed by projecting light from the lightsource through the transparent panel. There is a coating over thetransparent panel such that light transparency in the middle section ofthe long axis is higher than either side.

The coating can be deposited over the entire transparent panel. Thecoating can be deposited over the imaging section on the transparentpanel only. In addition, the coating can be made by forming a pluralityof coating materials of the same thickness over surface regions of thetransparent panel so that a range of light transparencies are obtainedacross the panel. Conversely, a coating made from a single material buthaving a variable thickness is formed across the transparent panel toobtain a range of light transparencies across the panel.

In this invention, a coating is added onto the transparent panel of anoptical sensor so that light transparency varies across the panel.Hence, there is no need to produce or modify components. Therefore, thisinvention is able to improve brightness variation of a light source withonly minimum modification of the components. In addition, theinstallation can be applied to other optical devices besides a scanner,such as a digital camera.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

FIG. 1 is a schematic structural diagram of an optical sensor systemaccording to one preferred embodiment of this invention;

FIG. 2a is a cross-sectional side view of the structure along line 2—2′of FIG. 1 according to a first embodiment of this invention;

FIG. 2b is a cross-sectional side view of the structure along line 2—2′of FIG. 1 according to a second embodiment of this invention;

FIG. 3a is a graph showing the variation of light transparency along thelong axis of the transparent panel due to the presence of the coating;

FIG. 3b is a graph showing the variation of brightness level along thelight axis of the light source; and

FIG. 3c is a graph showing the variation of brightness level after lightfrom the light source passes through the transparent panel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1 is a schematic structural diagram of an optical sensor systemaccording to one preferred embodiment of this invention. The systemincludes, a light source 10, a coating 15, a transparent panel 20 and asensor 25. The light source 10 is able to generate an image for sensing.The sensor 25, the transparent panel 20 and the coating 15 togetherconstitute the optical sensor. The transparent panel 20 is positionedbetween the sensor 25 and the light source 10. When the image producedby the light source is projected onto the transparent panel 20, a longaxis is created. The coating 15 is formed over one glass surface of thetransparent panel 20.

The sensor 25 detects the light image after light from the light source10 has passed through the coating 15 and the transparent panel 20. Thecoating 15 on the transparent panel 20 modifies the light transparencyalong the long axis such that the light transparency is lower in themiddle compared with either end.

The coating 15, as shown in FIG. 1, is formed only over the regionwithin the transparent panel 20 where the projected image produced bythe light source 10 is covered. In practice, the coating 15 may coverthe entire glass surface of the transparent panel 20.

FIG. 2a is a cross-sectional side view of the structure along line 2—2′of FIG. 1 according to a first embodiment of this invention. As shown inFIG. 2a, the coating 15 on the transparent panel 20 is formed using asingle material having a variable thickness along the long axis. Inother words, the thickness of the coating 15 near the middle is greaterthan the thickness along the two sides. Light transparency of thecoating 15 has a characteristic curve shown in FIG. 3a. In fact, FIG. 3ais a graph showing the variation of light transparency along the longaxis of the transparent panel due to the presence of the coating.

FIG. 3b is a graph showing the variation of brightness level along thelight axis of the light source. After light from the light source 10 ispassed through the transparent panel 20 with a single-layered coating15, variation of brightness level along the long axis is shown in FIG.3c. As shown in FIGS. 3b and 3c, brightness level after passing throughthe transparent panel 20 is much flatter and wider than the brightnesslevel along the light axis of the original light source 10. Since theoptical sensor relies heavily on brightness contrast to carry outdetection, the brightness curve shown in FIG. 3c is more suitable forimage detection than the curve shown in FIG. 3b.

FIG. 2b is a cross-sectional side view of the structure along line 2—2′of FIG. 1 according to a second embodiment of this invention. As shownin FIG. 2b, the coating 15 on the transparent panel 20 is actuallycomprised of three different coatings 15a, 15b and 15c, each having adifferent light transparency but identical thickness. All the coatings15a, 15b and 15c together produce a light transparency curve shown inFIG. 3a. In other words, light transparency in the middle is lowerrelative to the sides.

FIG. 3b is a graph showing the variation of brightness level along thelight axis of the light source. After light from the light source 10 ispassed through the transparent panel 20 with multiple coatings 15a, 15band 15c, variation of brightness level along the long axis is shown inFIG. 3c. As shown in FIGS. 3b and 3c, brightness level after passingthrough the transparent panel 20 is much flatter and wider than thebrightness level along the light axis of the original light source 10.Since the optical sensor relies heavily on brightness contrast to carryout detection, the brightness curve shown in FIG. 3c is more suitablefor image detection than the curve shown in FIG. 3b.

Note that the number of coatings on the transparent panel 20 is notlimited to three. To fit a particular design, the number of coatings canincrease and the type of material forming the coatings can vary.

In summary, the greatest benefit of this invention is the reduction ofbrightness variation of a light source without the need to produce newcomponents. In fact, only minor modifications of a single component areneeded.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. An installation for increasing the a usable range along the an axialdirection of a light source, comprising: a light source for generating asense image; and an optical sensor, wherein the optical sensor includesa sensor, a transparent panel and a coating, wherein the transparentpanel is positioned between the sensor and the light source, the coatingis formed over the transparent panel, the transparent panel has a longaxis running from edge to edge, the sensor detects an image after lightfrom the light source has passed through the coating and the transparentpanel, and the coating on the transparent panel modifies the lighttransparency along the long axis such that the light transparency islower in the middle compared with the ends.
 2. The installation of claim1, wherein the coating is formed only over the an image-forming regionwhen light passes through the transparent panel.
 3. The installation ofclaim 1, wherein the coating actually comprises of a plurality ofcoatings attached side by side with each coating material having adifferent light transparency.
 4. The installation of claim 1, whereinthe sensor includes a charge couple device (CCD).
 5. The installation ofclaim 1, wherein one application is the a scanner.
 6. An installationfor increasing the a usable range along the an axial direction of alight source, comprising: a light source for generating a sense image;and an optical sensor, wherein the optical sensor includes a sensor, atransparent panel and a coating, wherein the transparent panel ispositioned between the sensor and the light source, the coating isformed over the transparent panel, the transparent panel has a long axisrunning from edge to edge, the sensor detects an image after light fromthe light source has passed through the coating and the transparentpanel, and the coating on the transparent panel modifies the lighttransparency along the long axis such that the light transparency islower in the middle compared with the ends, wherein the coatingcomprises of a single coating material but a variable thickness alongthe long axis.
 7. An installation for increasing the a usable rangealong the an axial direction of a light source, comprising: a lightsource for generating a sense image; and an optical sensor, wherein theoptical sensor includes a sensor, a transparent panel and a coating,wherein the transparent panel is positioned between the sensor and thelight source, the coating is formed over the transparent panel, thetransparent panel has a long axis running from edge to edge, the sensordetects an image after light from the light source has passed throughthe coating and the transparent panel, and the coating on thetransparent panel modifies the light transparency along the long axissuch that the light transparency is lower in the middle compared withthe ends, wherein the coating comprises of multiple coating materialswith different light transparency but with an equal thickness along thelong axis.
 8. An apparatus, comprising: a sensor; a transparent panelpositioned over the sensor; and a coating formed on a surface of thetransparent panel, wherein the coating is configured to provide reducedtransparency at a middle portion of the coating relative to an edgeportion of the coating.
 9. The apparatus of claim 8, wherein the coatingcomprises a single coating material having a variable thickness.
 10. Theapparatus of claim 8, wherein the coating comprises a plurality ofcoating materials.
 11. A method, comprising: forming a coating on asurface of a transparent panel, wherein the coating is configured toprovide reduced transparency at a middle portion of the coating relativeto an edge portion of the coating; and positioning the transparent panelbetween a light source and a sensor.
 12. The method of claim 11, whereinforming the coating on the surface of the transparent panel comprisesforming a coating having a variable thickness.
 13. The method of claim11, wherein forming the coating on the surface of the transparent panelcomprises forming a coating comprising a plurality of coating materials.14. An apparatus, comprising: a light source; a sensor; a transparentpanel positioned between the light source and the sensor; and a coatingformed on a surface of the transparent panel, wherein the coating isconfigured to provide reduced transparency at a middle portion of thecoating relative to an edge portion of the coating.
 15. The apparatus ofclaim 14, wherein the coating comprises a single coating material havinga variable thickness.
 16. The apparatus of claim 14, wherein the coatingcomprises a plurality of coating materials.
 17. The apparatus of claim9, wherein the middle portion of the single coating material is thickerthan the edge portion.
 18. The method of claim 12, wherein the middleportion of the coating is thicker than the edge portion.
 19. Theapparatus of claim 15, wherein the middle portion of the single coatingmaterial is thicker than the edge portion.
 20. An apparatus, comprising:a sensor; a transparent panel positioned over the sensor; and a coatingformed on a surface of the transparent panel, wherein the coating isconfigured to provide reduced transparency at a portion of thetransparent panel disposed closer to a light source relative to aportion of the transparent panel disposed farther from the light source.21. The apparatus of claim 20, wherein the coating comprises a singlecoating material having a variable thickness.
 22. The apparatus of claim20, wherein the coating comprises a plurality of coating materials. 23.The apparatus of claim 20, wherein the transparent panel is disposedbetween the sensor and the light source.
 24. A method, comprising:forming a coating on a surface of a transparent panel, wherein thecoating is configured to provide reduced transparency at a portion ofthe transparent panel disposed closer to a light source relative to aportion of the transparent panel disposed farther from the light source;and positioning the transparent panel between the light source and asensor.
 25. The method of claim 24, wherein forming the coating on thesurface of the transparent panel comprises forming a coating having avariable thickness.
 26. The method of claim 24, wherein forming thecoating on the surface of the transparent panel comprises forming acoating comprising a plurality of coating materials.
 27. An apparatus,comprising: means for sensing light; a transparent panel positioned overthe light sensing means; and means for providing reduced transparency ata portion of the transparent panel disposed closer to a light sourcerelative to a portion of the transparent panel disposed farther from thelight source.
 28. An apparatus, comprising: means for producing light;means for sensing light; a transparent panel positioned between thelight producing means and the light sensing means; and means forproviding reduced transparency at a portion of the transparent paneldisposed closer to the light producing means relative to a portion ofthe transparent panel disposed farther from the light producing means.29. A digital camera, comprising: a sensor; a transparent panelpositioned over the sensor; and a coating formed on a surface of thetransparent panel, wherein the coating is configured to provide reducedtransparency at a portion of the transparent panel disposed closer to alight source relative to a portion of the transparent panel disposedfarther from the light source.
 30. The digital camera of claim 29,wherein the transparent panel is disposed between the sensor and thelight source.
 31. A scanner, comprising: a sensor; a transparent panelpositioned over the sensor; and a coating formed on a surface of thetransparent panel, wherein the coating is configured to provide reducedtransparency at a portion of the transparent panel disposed closer to alight source relative to a portion of the transparent panel disposedfarther from the light source.
 32. The scanner of claim 31, wherein thetransparent panel is disposed between the sensor and the light source.33. A method for increasing the usable range of a light source, themethod comprising: reducing a transparency of a first portion of atransparent panel relative to a transparency of a second portion of thetransparent panel, wherein reducing the transparency of the firstportion comprises using a coating material having a variable thicknesson the transparent panel.
 34. The method of claim 33, wherein the firstportion is a middle portion of the transparent panel and the secondportion is an edge portion of the transparent panel.
 35. The method ofclaim 33, wherein the first portion is a portion of the transparentpanel disposed closer to the light source relative to the secondportion.
 36. The method of claim 33, wherein reducing the transparencyof the first portion comprises using a plurality of coating materials onthe transparent panel.